Automatic or semi-automatic packaging machines are known to comprise means for feeding the packaging boxes along a guided path, for the sealing thereof by means of adhesive tape.
For guiding the box at its base, a supporting roller table, conveying and/or taping means, and lateral retention means are normally provided, these latter being generally in the form of parallel rods fixed at a distance apart equal to the box width. For guiding the box at its top, an upper conveying and/or taping head is used, to which are associated lateral retention means, generally in the form of pressure rollers mounted idly on vertical pins. These rollers can be moved vertically together with the head, in relation to the height of the boxes to be sealed. Their positon can also be adjusted transversely in relation to the box width.
The present invention is concerned with the problem of adjusting the position of the pressure rollers associated to the upper head. One of the most known methods for obtaining this adjustment is to mount the pin of each pressure roller on a clamp slidable along a support rod, which is welded on to the upper guide head of the machine so as to project in a transverse direction from a position of the head which is set back in respect of the box feed direction.
Although generally used in packaging machines of this type, this arrangement has some drawbacks. Firstly, mounting the rod on the upper head in a set-back position overloads the head itself, which becomes unbalanced about its transversal support axis. Furthermore, providing both a support rod welded to the head and a clamp which slides on said rod, involves considerable cost both in terms of manufacture and assembly.